func machoCodeSigSym(ctxt *Link, codeSize int64) loader.Sym {
	ldr := ctxt.loader
	cs := ldr.CreateSymForUpdate(".machocodesig", 0)
	if !ctxt.NeedCodeSign() || ctxt.IsExternal() {
		return cs.Sym()
	}
	sz := codesign.Size(codeSize, "a.out")
	cs.Grow(sz)
	cs.SetSize(sz)
	return cs.Sym()
}

// machoCodeSign code-signs Mach-O file fname with an ad-hoc signature.